The carpal tunnel is a narrow tunnel in the wrist formed by ligament and bone. Passing through the carpal tunnel is the median nerve, which carries impulses from the brain into the hand. Tendons in the hand which enable the hand to close also pass through the carpal tunnel. These tendons, when stressed, swell inside the carpal tunnel and compress the median nerve. Compression of the median nerve leads to numbness or weakness of the hand. Ultimately, if not treated, theses systems lead to carpal tunnel syndrome (CTS). CTS may be caused by a variety of factors. Activities that require the wrist to remain in extended, flexed or exaggerated positions for significant periods of time may lead to CTS.
The symptoms of CTS are a tingling, numbness of the hand between the thumb and part of the ring finger accompanied by pain that travels up the forearm from the wrist. There is a potential of permanent numbness and limited movement of the fingers associated with CTS. Subsequent treatment requires a splint to be worn about the wrist, cortisone injections and in some cases operations to relieve the pain.
CTS has become an increasingly significant problem as computers have become a mainstay in the home and in the office environment. Repetitive use of the computer mouse and other input devices has added to the problem. Handed versions of the mouse are designed specifically to the contours of either the right or the left hand. In use, the palm of the hand caresses the mouse with the Carpal Tunnel part of the hand squeezed in place by the flesh below the thumb (“Thenar Eminence”) and the flesh below the pinky (“Hypthenar Eminence”). Continued use of the mouse in this position causes the Carpal Tunnel to become very narrow which inflames tissues which then press against nerves which in turn cause pain, numbness and weakness, often resulting in CTS. Additionally, if a mouse, trackball or other input device is placed too far away, too high, too low, or too much on one side from the user the position can cause shoulder, wrist, elbow and forearm discomfort. Repetitive movement of the shoulder and arm often results in posture related problems other than CTS.
It has been postulated that improper wrist posture when using a computer keyboard or mouse has contributed towards the development of CTS. If the keyboard or mouse is placed on a flat surface such as a table, the user's wrist will be bent. Such bending of the wrist places significant stress on the wrist muscles. Solutions to mitigate wrist bending while using a mouse are known in the art. For example, U.S. Pat. No. 5,131,614 to Garcia discloses a wrist support for alleviating stress-related problems associated with the use of a computer mouse. U.S. Pat. No. 7,025,310 to Bouchard discloses a hand and wrist support device to be used with a mouse. The device is designed to allow operation of the mouse with the user's fingers with hand and wrist positioned on the device remaining on a horizontal plane, stationary and relaxed. In use, the user's wrist rests on an elevated surface that is adapted to accommodate the mouse.
U.S. Pat. No. 5,433,407, to Rice, which is incorporated by reference, also discloses an attachment to be used with a mouse that alleviates posture- and stress-related disorders associated with use of a mouse. The attachment described in U.S. Pat. No. 5,433,407 is a curved-shape palm rest that has a back and top portion and side walls. The walls form a cavity which is able to accept a portion of the mouse. The user's palm is placed on the palm rest which allows the fingers to control the attached mouse. According to U.S. Pat. No. 5,433,407, this position encourages an essentially straight path between the elbow, wrist and hand of the user, hence reducing wrist bend and stress to the carpal tunnel.
Accordingly, prior art methods of reducing CTS associated with the use of a mouse or other input device have relied on supporting the palm, wrist, forearm and/or shoulder to alleviate stress which is supposed to result is less fatigue. While the prior art methods have partially succeeded in alleviating or delaying symptoms associated with CTS, they have not addressed the underlying problem, that is, keeping the carpal tunnel open. In prior art methods described above, the palm is in direct contact with the ‘free’ mouse or the mouse attachment. For instance, in U.S. Pat. No. 5,433,407, the disclosed palm rest has a curvilinear upper section where the user rests his or her palm. The design allows the user's hand to conform to the shape of the palm rest. However, such a configuration provides little or no space between the palm of the hand and the palm rest. Moreover, as discussed with respect to the ‘free’ mouse, the carpal tunnel part of the hand in direct contact with the palm rest is squeezed in place, resulting in significant tunnel narrowing, ultimately leading to CTS and other posture related problems.
Thus, what is needed is a means of significantly alleviating or eliminating CTS and other stress-related disorders resulting from the use of a computer mouse and other input devices. The solution to the problem must be a device that is easy to use, comfortable, adaptable to various input devices, and addresses the underlying problems that result in CTS.